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https://issues.apache.org/jira/browse/NIFI-2039?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15363101#comment-15363101
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ASF GitHub Bot commented on NIFI-2039:
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Github user asfgit closed the pull request at:
https://github.com/apache/nifi/pull/601
> Provide ability to get InputStream from FlowFile without using Process
> Session callback
> ---------------------------------------------------------------------------------------
>
> Key: NIFI-2039
> URL: https://issues.apache.org/jira/browse/NIFI-2039
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Reporter: Mark Payne
> Assignee: Mark Payne
> Fix For: 1.0.0
>
>
> Provide a mechanism to obtain an InputStream for a FlowFile directly from the
> ProcessSession without having to provide an InputStreamCallback.
> Currently, we often have processors that create an AtomicReference so that
> the value can be set within a callback and then the value must be obtained
> using a get() once the callback returns. This is very un-intuitive.
> Additionally, we don't have the ability to return an InputStream to other
> code that may required to run in a callback. For instance, when using
> Calcite, Calcite wants a callback, essentially, that provides an Enumerator
> of data. We can't currently support this well because we can't create an
> InputStream and return it.
> We need to add the following method to ProcessSession:
> InputStream read(FlowFile flowFile) throws ProcessException;
> The InputStream that is returned must be tracked by ProcessSession such that
> when the session is committed or rolled back, the stream is closed if it
> hasn't been already. All of the logic that currently takes place in
> ProcessSession.read() after the callback returns must be done on the closing
> of the new InputStream that is returned.
> The MockProcessSession should throw an Exception if commit() is called
> without the InputStream being closed, ideally providing the stack trace of
> where the stream was obtained and where commit() was called. This is to
> ensure that the developer is being a good consumer, but the
> StandardProcessSession doesn't really need to do this, as we can simply close
> the InputStream so that it can no longer be consumed.
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